[Mingw-w64-public] "'_tzset' was not declared in this scope" when trying to build?

I'm trying to get MinGW 64 working with the Qt platform. But while configuring/building Qt I get the message"error: '_tzset' was not declared in this scope" (more specifically, "C:\Qt/src/corelib/tools/qdatetime.cpp:3768:12: error: '_tzset' was not declared in this scope") I initially thought this

[Mingw-w64-public] "cygwin1.dll was not found"? Also unzipping errors

I extracted mingw-w64-bin_i686-cygwin-1.5.25-15_20080908.tar.bz2 and placed it in the folder mingw64. However when trying to run C:\mingw64\bin\x86_64-pc-mingw32-g++.exe, I get the error: "x86_64-pc-mingw32-g++.exe - Unable to Locate Component "This application has failed to start because cygwin1.